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arXiv 1312.2189nucl-th
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$^{252}$ Cf和$^{236}$ U $^*$的真三元fission中团簇形成的特性

Peculiarities of clusters formation in true ternary fission of $^{252}$Cf and $^{236}$U$^*$

A. K. Nasirov, W. von Oertzen, A. I. Muminov, R. B. Tashkhodjaev

摘要:

通过对势能面(PES)景观的分析,讨论了一种新型团簇衰变“共线团簇三分”(CCT)的存在。三元体系的总能量是碎片的结合能和它们之间的核-核相互作用的总和。三元体系的预分裂态被假定为沿直线排列的三个碎片的链。PES的最小值和谷值由它们之间的质子和中子分布的变化确定。假定了裂变前瞬发中子发射,并计算了2- 4中子发射情况下的PES。对于$^{252}$ Cf的自发裂变和$^{235}$ U的中子诱发裂变的CCT计算的所有PES,对应于质量$A$ =130-136的Sn同位素的形成的谷的存在是固有的。存在局部最小值,其指示具有幻数质子或/和中子数(诸如20、28和50)的Ca、Fe、Ni、Ge和Se同位素的形成。分析表明,实验观察到的$^{68}$ Ni是在$^{236}$ U和$^{252}$ Cf裂变时,分别通过Si和Ca同位素与Sn连接的三元系的边缘碎片。

英文摘要:

The existence of a new type of cluster decay called "collinear cluster tri-partition" (CCT) is discussed by an analysis of the landscape of the potential energy surface (PES). The total energy of the ternary system is found as a sum the binding energies of fragments and nucleus-nucleus interaction between them. The pre-scission state of the ternary system is assumed to be arranged as a chain of the three fragments along a straight line. Minima and valleys of the PES are determined by variation of the proton and neutron distributions between them. Pre-scission prompt emission of neutrons is assumed and PES is calculated for the cases of emission of 2---4 neutrons. The presence of the valley corresponding to the formation of the isotopes of Sn with masses $A$=130---136 is inherent for all PES calculated for CCT for spontaneous fission of $^{252}$Cf and fission induced by neutrons of $^{235}$U. There are local minima indicating the formation of Ca, Fe, Ni, Ge and Se isotopes having magic proton or/and neutron numbers, such as 20, 28, and 50. The analysis shows that the experimentally observed $^{68}$Ni is formed as the edge fragment of the ternary system connecting to Sn by Si and Ca isotopes at fission of $^{236}$U and $^{252}$Cf, respectively.

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